‘Crazy ants’ invade southeastern U.S., displacing native species

Invading Tawny “crazy ants” from South America are displacing native fire ants across the southeastern United States and could have a dramatic impact on the region’s ecosystem, according to a new study. Native to northern Argentina and southern Brazil, the tawny crazy ant (Nylanderia fulva) was formally identified in 2012. Often referred to as Raspberry crazy ants, scientists have officially dubbed them “Tawny crazy ants.”

Although Tawny crazy ants do not sting humans like fire ants, they are far more intrusive, establishing super-colonies that push out local ant and arthropod populations. Sometimes they even take over entire homes.

“When you talk to folks who live in the invaded areas, they tell you they want their fire ants back,” co-author Ed LeBrun, a researcher at the University of Texas’ invasive species research program, told reporters.

The ants were first discovered in the U.S. in 2002 by a Houston pest control worker in a suburb of Houston and have since established populations in 21 counties in Texas, 20 counties in Florida, with a few colonies seen in southern Louisiana and southern Mississippi.

The “ecologically dominant” crazy ant is just the latest ant invasion from the southern hemisphere and is reducing diversity across a range of ant and arthropod species. Arthropods, which make up over 80 percent of the world’s living species, are invertebrates with exoskeletons and include spiders, millipedes, and wasps. The ants probably entered the U.S. through the Port of New Orleans, says LeBrun, as did the Argentine ant in 1891, the black fire ant in 1918, and the red fire ant in the 1930s.

LeBrun and his colleagues studied two crazy ant invasion sites on the Texas Gulf Coast and found that fire ant populations were eliminated where crazy ants were the densest. Other native ant populations were also eliminated or greatly reduced.

Tawny crazy ants are proving tough to control. They seem not to be affected by the same poisons used to eliminate fire ants and are tenacious, regenerating their mounds whenever they are destroyed.

“They don’t sting like fire ants do, but aside from that they are much bigger pests,” said LeBrun. “There are videos on YouTube of people sweeping out dustpans full of these ants from their bathroom. You have to call pest control operators every three of four months just to keep the infestation under control. It’s very expensive.”

Because the Tawny crazy ant requires humans to colonize new areas, the spread of the insect could be limited if people take measures to limit their transplantation, said LeBrun. “We can really make a difference,” he said, “but we need to be careful, and we need to know more.”

LeBrun and his colleagues published their research in the journal Biological Invasions.

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